#include <iostream>
#include <cstring>
using namespace std;

class CArray {
		int size;
		int *ptr;
	public:
		CArray(int s = 0);
		CArray(const CArray &a);
		~CArray();
		void push_back(int v);
		CArray &operator = (const CArray &a);
		int length() {
			return size;
		}
		int &operator[](int i) {
			return ptr[i];
		}
};

CArray::CArray(int s): size(s) {
	if (s == 0)
		ptr = NULL;
	else
		ptr = new int [s];
}

CArray::CArray(const CArray &a) {
	if (!a.ptr) {
		ptr = NULL;
		size = 0;
		return;
	}
	ptr = new int[a.size];
	memcpy(ptr, a.ptr, sizeof(int) * a.size);
	size = a.size;
}

CArray::~CArray() {
	if (ptr)
		delete[]ptr;
}

CArray &CArray::operator =(const CArray &a) {
	if (ptr == a.ptr)
		return *this;
	if (a.ptr == NULL) {
		if (ptr)
			delete [] ptr;
		ptr = NULL;
		size = 0;
		return *this;
	}
	if (size < a.size) {
		if (ptr);
		delete [] ptr;
		ptr = new int[a.size];
	}
	memcpy(ptr, a.ptr, sizeof(int)*a.size);
	size = a.size;
	return *this;
}

void CArray::push_back(int v) {
	if (ptr) {
		int *tmpPtr = new int[size + 1];
		memcpy(tmpPtr, ptr, sizeof(int)*size);
		delete[ ]ptr;
		ptr = tmpPtr;
	} else
		ptr = new int[1];
	ptr[size++ ] = v;
}

int main() {
	CArray a;
	for ( int i = 0; i < 5; ++i)
		a.push_back(i);
	CArray a2, a3;
	a2 = a;
	for ( int i = 0; i < a.length(); ++i )
		cout << a2[i] << " ";
	a2 = a3;
	for ( int i = 0; i < a2.length(); ++i)
		cout << a2[i] << " ";
	cout << endl;
	a[3] = 100;
	CArray a4(a);
	for (int i = 0; i < a4.length(); ++i)
		cout << a4[i] << " ";
	return 0;
}